Monday, November 14, 2011

Last week an asteroid known as 2005 YU55 zoomed past the Earth at a distance closer than the Moon. Imagine if astronomers knew about a similar asteroid that would actually impact the Earth sometime in the next few decades, but they decided not to discuss it with the people of the world. The public would understandably be outraged at such a cover-up -- they would demand to know the details of when and where the asteroid would strike our planet, and the likely consequences for the survival of the human race. Although this example is fictional, it is precisely the situation faced by climate scientists who are currently not talking about the unavoidable consequences of climate change during the next 50 years.

The release of too much heat-trapping pollution into the Earth's atmosphere is like an ecological deficit that we pass to future generations, and the gradual accumulation of this pollution is our climate debt. The choices of our parents and grandparents resulted in the release of so much carbon-dioxide that it exceeded the capacity of the Earth's natural systems -- primarily the oceans and forests -- to absorb it. The surplus pollution from each year remains in the atmosphere, and commits us to some amount of climate change for as long as it takes the planet to work through the accumulated excess. Even if we eliminated all human-induced sources of this pollution right now -- like coal-burning power plants and gasoline-powered automobiles -- the globe would continue to warm significantly for at least the next 50 years. This fact is not a secret, but the implications are so devastating that climate scientists generally prefer to discuss what we can do to "avoid the worst consequences of climate change" so that people will be less likely to feel overwhelmed.

Since the industrial revolution, the average temperature on the surface of the Earth has increased by about 1 degree centigrade. Knowing how much extra heat-trapping pollution is already in the atmosphere, and looking at the geological record of how temperature and carbon-dioxide empirically change together, scientists know that we are already committed to additional warming of 1-2 degrees centigrade over the next 50 years. Our decisions now about how to respond to the threat of climate change will only affect how much warmer the planet will get, and how long it will take to return to its normal temperature during the lives of our children and grandchildren. There is a significant moral difference between our actions and those of previous generations, because we now know with certainty what our choices are doing to the atmosphere and we are collectively making a conscious decision that will determine the type of world we will leave for our progeny. Considering the extreme weather events that have already resulted from 1 degree of warming -- hurricanes, tornadoes, drought and flooding -- the prospects for the next 50 years already look bleak, even if we manage to stop digging the hole deeper within our lifetimes.

Although it can be depressing to focus on the unavoidable consequences of climate change, it is important to remember that we still have the power to save the future. Our generation will certainly need to adapt to a warmer world, but we can also take steps in the short term to minimize the impact of the current climate debt. There are a variety of options for countering the warming effect of the excess carbon-dioxide in the atmosphere, from simple actions like planting more trees to more aggressive responses like artificially enhancing the capacity of the ocean to absorb heat-trapping gases, or injecting sulfates into the upper atmosphere to reduce the amount of energy the Earth's surface receives from the Sun. These are just short term strategies -- even if we can temporarily regulate the temperature of the planet, the excess carbon-dioxide will still acidify the oceans and disrupt fragile ecosystems -- but they could potentially help us make the transition to a clean-energy future at a lower financial and ecological cost.

Scientists should level with the public about the climate change we will experience over the next 50 years. Just like an asteroid on an impact trajectory, the longer we wait to respond to the problem the harder it becomes to avoid a disaster. Unlike an asteroid, part of the climate disaster is unavoidable. With a better understanding of the impacts we are already facing, the citizens of the world can demand a response.